The present invention relates generally to a device for sealing and perforating a thermoplastic film folded back on itself. The invention specifically relates, but not exclusively so, to the manufacture of perfusion pouches or bags.
Machines for the manufacture of pouches from a flexible film of plastic material are known. Particularly, there are known machines for the manufacture of pouches from a thermoplastic film. These machines include a series of stations at which the film is treated in succession. Generally, the film is unwound from a winding device, then it is perforated. Perpendicular to the perforations, ports or fitments are heat sealed by a welding head then the film is shaped in a shaping device principally designed to fold the film back on itself in order to create an edge to edge heat seal. The film thus sealed edge to edge forms a tube that is then sealed in the transverse direction at regular intervals, to create individual pouches or bags. These individual pouches are then filled prior to the sealing of the pouch or bag.
A present invention more particularly relates to a device designed to create the edge to edge heat sealing of the film folded back on itself.
Devices are known that permit the creation of a seal parallel to the edge, or even two seals parallel to the edge and spaced from each other, in order to form a small protruding edge inside which a perforation can be made to create an opening to hang the pouch. The seal or seals generally are created by use of a sealing strip that comprises a heating portion. The film so sealed, is allowed to cool naturally at the exit of the sealing station. Such a structure presents several drawbacks, especially in machines working at high speeds, wherein the sealing strips must be brought to a high temperature in order to create a rapid sealing. Indeed in such machines, there exists a risk that the stresses exerted on the film as it exits the sealing station will cause a separation, at least partial, of the associated film portions, so that the seal no longer is secure or is too fragile.